The company, which has 320 million active users, tweeted that it is aware of the issue and is trying to fix it. The announcement was sent at 0841 GMT.
Users said the service was not accessible on desktop computers. Twitter's blog posts, corporate info and most other pages on the Twitter.com website were also inaccessible, displaying the blue error screen.
Twitter's mobile app was partially functioning for some users but its timeline updated new tweets sporadically. Its search function appeared disabled as some hashtags or keyword searches returned no results. Users' profile pages appeared to be accessible from the mobile app.
Third party services, such as the TweetDeck service, also returned a blank page.
Twitter has suffered several service disruptions so far this year. On Monday, some users could not access Twitter on mobile and web for about 10 minutes. The service was disrupted on Friday for about 20 minutes.
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